The file /etc/ppp/ip-up.ipv6to4 is actually a copy of /etc/ppp/ipv6-down. This is because of what appears to have been some finger trouble in the last commit: https://src.fedoraproject.org/rpms/ppp/c/bb986960 The line in the spec where /etc/ppp/ip-up.ipv6to4 is installed has been changed to use the wrong source file, resulting in an extra copy of the ipv6-down script being included in its place.
This was fixed in https://src.fedoraproject.org/rpms/ppp/c/332d094cb4